Normally the hair around the nipples falls out before delivery. and thr kittens will soon wear it off anyway. I have never shaved a pregnant cat - I would be too afraid of cutting her nipples.
Some long hair breeders do clip away the fur, so kittens nails don't create tangles. This is done by sliding a comb underneath and cutting along the top - no risk to nicking any skin that way.
But it's not required, and hair will fall away from around the nipples.